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Building Envelope A building envelope includes all the components that make up the shell or skin of the building. These components separate the exterior of the building from the interior, and are designed by the project architect or engineers to meet the needs of each individual application. The building envelope may also be defined as the components that separate conditioned areas from unconditioned space. Exterior or unheated living spaces are not included inside the envelope, while any living space that is equipped with heat or air conditioning would be included. The building envelope must be carefully designed with regard to climate, ventilation, and energy consumption within the structure. There are four basic functions of the building envelope. These include adding structural support, controlling moisture and humidity, regulating temperature, and controlling air pressure changes. By serving these different functions, the envelope also affects ventilation and energy use within the building. The envelope is made up of all of the exterior components of the building, including walls, roofing, foundations, windows, and doors. Finish materials like siding and decorative items are not usually considered a part of the envelope. Insulation, building paper, and other components aimed at controlling moisture and airflow are typically included in the building envelope design. Building envelopes are often characterized as "tight" or "loose." A tight envelope is precisely constructed to allow relatively few air leaks. This often requires significant quantities of insulation, caulk, sealants, and energy-efficient windows to create a tight shell for the building. Loosely-constructed envelopes allow air to flow more freely from the exterior to interior spaces. A loose envelope may be created by design, or may be the result of poor construction techniques. Many experts debate the benefits of tight versus loose building envelopes. A tight envelope allows for a high level of control over indoor air quality, energy consumption, temperature, and humidity levels. It leads to fewer drafts and a more comfortable environment for occupants, and often results in less waste in heating and cooling costs. Tightly-designed envelopes also reduce the likelihood of mold or mildew caused by moisture infiltration, which may prolong the life of building components. At the same time, tighter buildings also limit how much natural ventilation can occur, which leads to more extensive mechanical ventilation requirements. A loosely-constructed building envelope allows natural air transfers to occur, which improves indoor air quality and often eliminates the need for mechanical ventilation. At the same time these looser buildings tend to be more drafty and uncomfortable, and can make it difficult to regulate temperature levels. There is an increased chance of moisture-related mold, and higher quantities of heated or cooled air are able to escape through leaks in the envelope. This can increase energy bills and negatively impact the environment by increasing greenhouse gas levels. Air-Conditioning System By having air-con ventilation from the ground, it saves energy. Cool air is not needed at the ceiling, thus by having ventilation pumps which give out cool air from the floor will be sufficient to cool the surrounding temperature of the room at the bottom. Hot air and cool air does not mix, hot air rises and cool air sinks due to differences in density, therefore, making the room cooler. Natural Ventilation Definition Natural ventilation is the process of supplying and removing air through an indoor space by natural means, meaning without the use of a fan or other mechanical system. It uses outdoor air flow caused by pressure differences between the building and its surrounding to provide ventilation and space cooling. Benefits of Natural Ventilation The use of natural ventilation is definitely an advantage with the raising concerns regarding the cost and environmental impact of energy use. Not only does natural ventilation provide ventilation (outdoor air) to ensure safe healthy and comfortable conditions for building occupants without the use of fans, it also provides free cooling without the use of mechanical systems. When carefully designed, natural ventilation can reduce building construction costs and operation costs and reduce the energy consumption for air-conditioning and circulating fans. An additional bonus is that no longer will any noisy fan be of your concern. Types of Natural Ventilation and their Design Considerations. There are basically two types of natural ventilation that can be employed in a building: wind driven ventilation and stack ventilation. Both of which are caused by naturally occurring pressure differences. However, the pressure differences that cause wind driven ventilation uses the natural forces of the wind where as stack ventilation is caused by pressures generated by buoyancy as a result in the differences in temperature and humidity. Hence, there are different strategies in the optimization of the two types of natural ventilation. Wind Driven Ventilation As naturally occurring wind blows across a building, the wind hits the windward wall causing a direct positive pressure. The wind moves around the building and leaves the leeward wall with a negative pressure, also known as a sucking effect. If there are any openings on the windward and leeward walls of the building, fresh air will rush in the windward wall opening and exit the leeward wall opening to balance and relieve the pressures on the windward and leeward walls. To capture the wind and bring ventilation to the building, the building shape becomes a crucial factor. The building shape can create wind pressures that can effectively drive the air flow through the openings of the building. There are of course many other factors that play into place. Recommendations from design guidelines from various building regulations also suggest the following: *Building orientation and location. (Choosing a location with a lot of wind, building should be oriented so that the windward wall is perpendicular to the summer wind. This is when you want to maximize the ventilation); *Building form and dimensions. (Naturally ventilated buildings should not be too deep because it will be more difficult to distribute fresh air to all portions of the building); *Window typologies and operations; *Types, shape and size of openings; *Construction methods and detailing; *External elements *Urban planning consideration Stack Ventilation Buoyancy ventilation can be induced by temperature (known as stack ventilation) or by humidity (known as cool tower). Most commonly used is the stack driven ventilation. For stack ventilation to work properly there must be a temperature difference. As the warm air (usually given off by the occupants and their computers), which is less dense, in the building rises, the cooler air is sucked from the openings below. This is shown in the picture below. Design considerations for stack ventilation *inlets should supply air low in the room. Outlets should be located across the room and at high level. *the vertical distance between the inlet and exhaust openings should take advantage of the stack effect. *Use skylights or ridge vents. *The function as fire exits of enclosed staircases should not be compromised if stack ventilation is incorporated into the design. With stack ventilation, it does not rely on the wind. On hot summer days with no wind, the naturally occurring stack effect can take place with relatively stable air flow. Moreover, because it does not rely on the pressure and direction of the wind, there is a greater control on locating the air intake. However, stack driven ventilation is limited to a lower magnitude than wind driven ventilation. It is also very dependent on the inside and outside temperature differences. Design Strategies for Natural Ventilation The design for natural ventilation should incorporate maximizing both the wind and stack driven ventilation design concepts as mentioned above. General design considerations include: *Increase air supply intake by ensuring no outside obstruction (such as vegetation or site objects) nor inside obstruction (such as furniture and interior partition) obstruct inlet openings; *Rooms should have inlet and outlet openings located in opposing pressure zones. This can include openings on the windward and leeward walls or on the windward wall and roof; *All occupied spaces should have an inlet and outlet opening in which at least a minimum of one opening should be an operable window to control flow; *Inlets should supply air at a location low in the room. Outlets should be located across the room and at a higher level; *The long facade of the building and the majority of the openings should be should be directed so that the windward wall is perpendicular to the summer wind; *Use skylights or ridge vents. They are very desirable for night time thermal comfort in houses to vent heated/warm air that rises, and allow heat to be radiated into the cold. It is also can be a good outlet for wind driven ventilation; *At least 3m allowance for the floor to ceiling. *window areas should not be excessive and be protected by exterior shading devices; *Design for high thermal capacity and exposed ceilings for night cooling. *Reduce the possibility of wall warming by the sun through use of light-coloured building exteriors, trees/shrubs to provide shading and evaporative cooling, grass and other groundcover to keep ground temperatures low, and ponds and fountains to enhance evaporative cooling; and *Internal loading should be kept low. Many of the considerations taken above is to either increase the air flow or lower the heat gain so that the natural ventilation can effective cool the spaces in the building. Mechanical cooling and ventilation systems will be used to supplement the natural ventilation. By lowering the heat gains, the less air flow will be required to remove the heat, thus there will be less a need of a mechanical cooling system. Designing a Ventilation System In order to build a more reliable and also cost and energy efficient ventilation system, one must identify the constraints of the building a nd utilize various design strategies such as those mentioned above and integrate it into the building design. The constraints may include, but is not limited, to the following: *Building type; *Local environment; *Climate; and *Building regulations/guidelines. Building type usually refers to the occupancy, possible building orientation and shape as well as possible size and location of openings. Local environment can refer to the prevailing wind direction, local air quality and surrounding structures. Climate refers to the local temperature and humidity. And finally building regulations/guidelines refer to local regulations, standards (such as ASHRAE) or guidelines. Design codes often specify certain ventilation rates. Ventilation rates encompass the maximum allowance concentration of contaminants, heat generation, and air change rates. Knowing these rates, one can determine the sizes of fans, openings, and air ducts. Below are Table 1 and Table 2 that illustrate the recommended air change rat es and outdoor air requirements respectively. Table 1 Recommended Air Change Rates (Source: Chartered Institute of Building Services Engineers Guide B) Table 2 Outdoor air requirements for ventilation from ASHRAE Standard 62-2004, Ventilation for Acceptable Indoor Air Quality Mechanical Ventilation A building ventilation system that uses powered fans or blowers to provide fresh air to rooms when the natural forces of air pressure and gravity are not enough to circulate air through a building. Mechanical ventilation is used to control indoor air quality, excess humidity, odours, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates specialised ventilation systems can remove excess moisture from the air. Ceiling fans are commonly seen as ventilation systems as they are usually the most visible mechanical system in a building; however ceiling fans do not provide real ventilation, as there is no introduction of fresh air. Ceiling fans only circulate air within a room for the purpose of reducing the perceived temperature by method of evaporation of perspiration on the skin of the occupants. Also hot air rises therefore; ceiling fans may be used to keep a room warmer in the winter by circulating the warm from the ceiling to the floor. MAIN METHODS OF FORCED VENTILATION: PRESSURE SYSTEM: a system which air is blown through the building by a fan or other blower placed at the inlet. The air pressure in the building is slightly greater than that of the outer atmosphere. VACUUM SYSTEM: causing an inrush of fresh air. This is done by an exhaust fan placed at the outlet to the vent flue or stack. The air pressure in the building is slightly lower than that of the outer atmosphere. However a combination of these two methods can be used to create a BALANCED SYSTEM: BENEFITS OF BALANCED SYSTEM: *Improved indoor air quality. Balanced ventilation systems supply fresh air to the living and sleeping areas of homes while exhausting stale air at an equal rate from the bathrooms. This proactive approach to ventilation can result in improved indoor air quality. *Improved comfort. Buildings with tight construction and balanced ventilation systems can have fewer drafts and a constant supply of outdoor air resulting in improved comfort. *Improved health. Stale air can cause health problems. It can be responsible for symptoms such as headaches, drowsiness, and respiratory problems. These symptoms are more common in homes with poor ventilation and moisture control. Continuously providing fresh air can result in the improved health and well being of the occupants. *Lower utility bills. Less energy is consumed to operate ventilation systems than to heat and cool excessive amounts of outdoor air that infiltrates leaky homes. Additional savings are captured when these systems are equipped with either a sensible or total heat exchanger. This can result in lower utility bills, making homes less expensive to operate. *Balanced ventilation systems can be equipped with a heat exchanger that recovers most of the heating and cooling energy from the exhaust air. Mechanical ventilation and natural ventilation have many applications where they are used, but in most modern intelligent design both are used for the best effectiveness and efficiency. Ventilation in Buildings Ventilation is the process by which fresh air moved around the building. Good ventilation is essential for the comfort and safety of building occupants, and in many cases subject to a legal minimum requirement. Ventilation methods Ventilation can be provided through a number of methods, the most energy efficient being a natural ventilation strategy. This requires specific design features to be included within the building to ensure that there is a source of fresh air and a path for a measured amount of stale air to escape. The simplest form of natural ventilation is through open windows, or through window trickle vents. Where a natural ventilation strategy is not possible either due to increased air flow rates required, or a demand for cooling, mechanical ventilation or a full air conditioned strategy is required. This is much more energy intensive due to the nature of the equipment (e.g. Fans) required to move air around the building. It is possible to mix a natural and mechanical ventilation strategy to achieve 'mixed mode' striking a balance between energy performance and comfort. Higher densities of people, IT equipment and lighting contribute to heat gain which requires ventilation to remove stale air, maintaining a measured level of fresh air supplied to a building. In order to maintain a desired temperature heating and cooling systems have to work harder with an ineffective ventilation system in place. Air Changes The replacement of a quantity of air in a space within a given period of time, typically expressed air changes per hour. If a building has one air change per hour, this is equivalent to all of the air in the building being replaced in a one-hour period. Under current regulations (Part F) an air change rate of 8 litres per second must be achieved for new build offices. Chilled Beams A chilled beam is a building cooling device that circulates air using the principles of natural heat convection. The major advantage of a chilled beam over more common forced air systems is that it circulates building air without the noise and expense of ductwork and air handlers. Typically mounted overhead near or within a ceiling, the beam is a type of radiator, chilled by an external source such as Recirculated water. It cools the space below it by acting as a heat sink for the naturally rising warm air of the space. Once cooled, the air naturally drops back to the floor where the cycle begins again. Condenser A condenser is a heat exchanger in which the refrigerant, compressed to a hot gas, is condensed to liquid by rejecting heat to achieve a cooled space. The condenser in an air conditioning unit is very similar to that used in a common refrigerator. Constant Air Volume (CAV) Constant Air Volume (CAV) is a type of heating, ventilating, and air-conditioning (HVAC) system. In a simple CAV system, the supply air flow rate is constant, but the supply air temperature is varied to meet the thermal loads of a space. Most CAV systems are small, and serve a single thermal zone. However, variations such as CAV with reheat, CAV Multizone, and CAV primary-secondary systems can serve multiple zones and larger buildings. Convection Heating In convection heating, air is heated when it comes into contact with hot surfaces in the heater. People feel warmer because of the higher air temperature. Some convection heaters use a fan to draw the cool air in. Fan Coil System A Fan coil system is an air conditioning system used in buildings. A fan unit is placed at each place which needs to be heated or cooled. A central plant delivers hot or cold water to fan units. The fan draws air from the room, blows it over the water coil and returns it to the room. Dehumidified air from a central plant or fresh air from outside may also be used by a fan coil system. Internal Environment In the context of mechanical building services the internal environment refers to the strategy employed to heat, cool and distribute air around a building. The Internal environment can be heated and/or cooled, whilst air distribution could be through natural or mechanical methods, or a mixture of the both for a mixed-made strategy. If comfort cooling is provided throughout the internal environment would be fully air conditioned. Mixed Mode A mixed mode system combines the best aspects of both natural ventilation and mechanical ventilation/air conditioning. The simplest example of a mixed mode system is the opening of windows to enable natural ventilation with air conditioning available when windows can not be opened. Natural Ventilation Ventilation systems are considered natural if the air is supplied and removed from the indoor space by non mechanical means. The use of natural ventilation reduces the need for mechanical energy consuming plant and is therefore more efficient. The requirement for natural ventilation to be utilised effectively in a building calls for early implementation in the design of a building. Radiant Heating Radiant heating heats a building through radiant heat. The heat energy is emitted from a warm element (floor, wall, overhead panel) and warms people and other objects in rooms rather than directly heating the air. The internal air temperature for radiant heated buildings may be lower than for a conventionally heated building to achieve the same level of body comfort (when adjusted so the perceived temperature is actually the same). Terminal Unit A terminal unit is the final device in an air conditioning system located in the space being heated or cooled. The terminal unit can be utilised to determine the flow and direction of air whilst re-heating/re-cooling to achieve the desired local temperature. Variable Air Volume (VAV) Variable air volume (VAV) is a technique for controlling the capacity of a heating, ventilating, and/or air-conditioning (HVAC) system. The simplest VAV system incorporates one supply duct that, when in cooling mode, distributes approximately 55 degree F supply air. Because the supply air temperature, in this simplest of VAV systems, is constant, the air flow rate must vary to meet the rising and falling heat gains or losses within the thermal zone served. Variable Speed Drive (VSD) An electronic device designed to be used with a motor to provide a variable flow output, thus reducing the energy required to turn the motor. Day-lighting Introduction Daylighting provides the opportunity for both energy savings and improved visual comfort. With proper integration of a well-designed artificial lighting system, daylighting can offer significant energy savings by reducing a portion of electric lighting load. An extra benefit is the lowering of cooling load due to the reduction in heat gain from electric lamps. In addition to energy savings, daylighting helps create visually pleasing and productive environment for building occupants. Daylight may be introduced into a building using a variety of design concepts or strategies. In addition, the design of windows influences the effectiveness of daylight utilization significantly. The daylight design can also be integrated with the artificial lighting system to achieve better energy efficiency. If all these factors are well-coordinated, the benefits of using daylight will be maximized. Daylighting strategies Daylighting strategies can be divided into two main categories: sidelighting and toplighting strategies. The key difference of the two strategies is that sidelighting admits light from the perimeter walls of the building while toplighting strategies admit light through the top of the building. The selection of daylighting system will depend on the layout, the orientation and the surroundings of the building. (a) Sidelighting Sidelighting is a technique that provides daylight through apertures located in the perimeter walls of a building. Those apertures include curtain wall or other continuous fenestration systems. In order to maximize the daylight penetration and reduce window glare, it is a good practice to separate the view aperture from the daylight aperture. For this reason, the daylight glazing are placed as close to the ceiling as possible for bouncing daylight deep into the room by the ceiling. In this way, higher visible transmittance glazing can be used in the daylight aperture. The following figure illustrates a standard sidelight concept. The accessibility of daylight in sidelighting strategy is highly dependent on building's facade orientation. Well-oriented apertures can maximize the daylight harvesting potential as well as minimizing glare and solar heat gain. Orienting the long axis of the building in the east/west direction will maximize the amount of northern and southern facades. The area of east and west openings can be minimized to reduce direct sunlight (glare) entering the building. (b) Toplighting Toplighting strategies provide daylight through rooftop apertures. These strategies can provide uniform daylight distribution to the entire top floor area if the entire top floor uses rooftop apertures distributed across the roof area. Large single level floor areas and the top floor of multi-story buildings can benefit from toplighting. The general types of toplighting include roof monitors, sawtooth roofs, and skylights. The figure below provides illustrations of these three basic toplighting strategies. Different types of daylighting strategies: a) roof monitors; b) saw tooth roof; c) skylights i) Roof monitors A roof monitor consists of a flat roof section raised above the adjacent roof, with vertical glazing on at all sides of the raised bay. This arrangement can provide daylight in all directions, but may result in higher heat gain. ii) Sawtooth roofs Sawtooth roofs employ a series of either vertical or sloped glasses, which are separated by sloped roof elements. Sawtooth roof can be used to uniformly illuminate a large floor area while minimizing impacts on building's overall height. The orientation of the glazing can be selected so as to maximize daylight level while reducing direct solar radiation and heat gain. iii) Skylights Skylights can have many forms including dome, pitched and flat panels that are placed in the plane of the building's roof. Horizontal skylights can be an energy problem because they receive solar heat directly at the midday. Integration of louver systems can control solar heat gain as well as glare in skylight. Utilization of light tubes In addition to the above strategies, daylight can be brought into the indoors by using light tubes. Light tube is device used to capture daylight and reflect it into the building. It consists of an outside collector (usually on the roof), a tube with high reflectance on the internal surface and a diffuser. By using light tubes, daylight can not only be reached the perimeter zones but also the deep regions of the rooms. More details of light tubes can be found in the website of This web page has hyperlinks which may transfer you to third-party website.Energy Efficiency Technology Daylight design considerations A number of factors should be considered during the design process of daylighting systems. These factors are briefly described below. (a) Aperture location In determining the location of aperture for daylighting, the proportions of rooms are rather important. A room that has high ceiling will have deeper penetration of daylight whether from sidelighting or toplighting. Higher window position will also result in deeper penetration and more even illumination in the room. Small windows separated by wall area will result in uneven illumination and unpleasant contrast between window and adjacent wall surfaces. (b) Reflectance of room surface Reflectance values for room surfaces will significantly affect daylight performance and should be kept as high as possible. The most important interior surface for light reflecting is ceiling. The ceiling reflectance value should be maintained at 0.8 or higher. In small room, the rear wall is the next important surface because it is directly facing the window. The suggested room surface reflectance values are list below: © Integration with artificial lighting control A successful daylighting design not only optimizes architectural features, but also integrated with the artificial lighting system so that the benefits from daylighting can be maximized. When daylight is sufficient to provide the required light level on working plane, corresponding lamps can be dimmed or switched off. It is now commonly to use occupancy and light level sensor to control the artificial lighting system. Please also refer to the website of Energy Efficiency Technology (link to http://ee.emsd.gov.hk Lighting > Technology Outline > Control systems) for more information on lighting control. (d) Artificial lighting design coordination The coordination of artificial lighting with the daylighting design is important for the success of the system. The layout and circuiting of the artificial lighting should be well-coordinated with the position of windows. For example, in a typical sidelighting design with windows along one wall, it is best to place the luminaries in rows parallel to the window wall and circuited so that the row nearest the windows will be the first to dim or switch off followed by successive rows. Artificial Lighting LED lighting LEDs (Light Emitting Diodes) are solid light bulbs which are extremely energy-efficient. When first developed, LEDs were limited to single-bulb use in applications such as instrument panels, electronics, pen lights and, more recently, strings of indoor and outdoor Christmas lights. Manufacturers have expanded the application of LEDs by "clustering" the small bulbs. The first clustered bulbs were used for battery powered items such as flashlights and headlamps. Today, LED bulbs are made using as many as 180 bulbs per cluster, and encased in diffuser lenses which spread the light in wider beams. Now available with standard bases which fit common household light fixtures, LEDs are the next generation in home lighting. A significant feature of LEDs is that the light is directional, as opposed to incandescent bulbs which spread the light more spherically. This is an advantage with recessed lighting or under-cabinet lighting, but it is a disadvantage for table lamps. New LED bulb designs address the directional limitation by using diffuser lenses and reflectors to disperse the light more like an incandescent bulb. Long-lasting - LED bulbs last up to 10 times as long as compact fluorescents, and far longer than typical incandescents. Durable - since LEDs do not have a filament, they are not damaged under circumstances when a regular incandescent bulb would be broken. Because they are solid, LED bulbs hold up well to jarring and bumping. Cool - these bulbs do not cause heat build-up; LEDs produce 3.4 btu's/hour, compared to 85 for incandescent bulbs. Common incandescent bulbs get hot and contribute to heat build-up in a room. LEDs prevent this heat build-up, thereby helping to reduce air conditioning costs in the home. Mercury-free - no mercury is used in the manufacturing of LEDs. More efficient - LED light bulbs use only 2-17 watts of electricity (1/3rd to 1/30th of Incandescent or CFL). LED bulbs used in fixtures inside the home save electricity, remain cool and save money on replacement costs since LED bulbs last so long. Small LED flashlight bulbs will extend battery life 10 to 15 times longer than with incandescent bulbs. Cost-effective - although LEDs are initially expensive, the cost is recouped over time and in battery savings. LED bulb use was first adopted commercially, where maintenance and replacement costs are expensive. But the cost of new LED bulbs has gone down considerably in the last few years. and are continuing to go down. Today, there are many new LED light bulbs for use in the home, and the cost is becoming less of an issue. To see a cost comparison between the different types of energy-saving light bulbs, see our Light Bulb Comparison Charts. Light for remote areas and portable generators - because of the low power requirement for LEDs, using solar panels becomes more practical and less expensive than running an electric line or using a generator for lighting in remote or off-grid areas. LED light bulbs are also ideal for use with small portable generators which homeowners use for backup power in emergencies. Lifts and Escalators Technology outline & How it can save energy http://ee.emsd.gov.hk/english/lift/lift_tech/images/images001.jpg Operating characteristics of different motor drives. The text below describes the image. Operating characteristics of different motor drives A variable speed drive system employs frequency inverter technology which rectifies AC voltages from the mains supply into DC, and then converts this into AC voltage with variable amplitude and frequency (i.e. VVVF control). The motor is thus supplied with variable voltage and variable frequency which enable infinitely variable speed regulation. In lift applications, VVVF control regulates input voltage and frequency to the motor throughout the journey. The figures below illustrate the variation of electrical current drawn by different lift motor drives during the whole journey of a lift car. The speed of the lift increases (accelerates) and decreases (decelerates) gradually at the beginning and ending respectively of the journey as shown in the top graph. When compared with AC 2 speed drive (middle graph) and ACVV drive (bottom graph), VVVF drive draw much less current during acceleration and deceleration. In escalator applications, VVVF control can be incorporated with automatic start/stop control or automatic two-speed control to vary the escalator speed according to the passenger flow. The operation of these kinds of escalator is determined by the presence or absence of passengers, hence energy can be saved when the escalator is idle. How much energy can be saved In lift applications, variable speed drives can reduce peak motor starting currents by as much as 80% compared with conventional motor drives. Further, wear and tear of the equipment can also be reduced during start/stop of the motor by using VVVF motor drive. Energy optimizer for lift and escalator ''' Technology outline & how it can save energy: The energy optimizer (also known as performance controller, energy saver or power factor controller) is a solid-state controller that reduces losses in AC induction motors in the form of energy efficiency and soft starting capability. It is not a variable speed drive and does not change the frequency of the motor. During the low load condition, induction motors usually operating at full supply voltage have very low power factor and are less efficient. The energy optimizer could provide the required motor operating voltage to suit various loading conditions, resulting in power factor improvement and reduction of motor losses. The other benefit of the energy optimizer is its soft starting property that reduce motor starting current and excessive wear of mechanical gears, chains, belts etc. associate with the mechanical transmission system. The energy optimizer could be use for any AC motor application with constant speed and variable load. Best applications are those motors with substantial variation in loading such as escalator and passenger conveyers. '''How much energy can be saved The amount of energy saving due to the energy optimizer in lift and escalator applications depends on the actual load of the lift or escalator. Based on the measurement of a retrofit project in a government office carried out by Electrical and Mechanical Services Department, the average energy saving can be up to 10% by using the energy optimizer. Service-on-demand escalator 'Energy optimizer for lift and escalator ' Technology outline: Modern escalator systems can be designed to detect passenger presence and stop when no activity has been detected for a period of time. The system will only be re-started automatically once a passenger has been detected. Since the operation of the escalator is determined by the presence or absence of passengers, it is known as "service-on-demand" (SOD) escalator. There are basically two types of SOD escalator. (a) Automatic start/stop control When an approaching passenger is detected, the escalator will start running and complete the traveling cycle. The escalator will stop after a period of time when no further passenger is detected. (b) Automatic two-speed control (crawl mode) Similar to the arrangement of auto on-off controlled escalator, the auto two-speed control SOD escalator will be actuated by the presence of passenger to run at rated speed. The auto two-speed controlled SOD escalator will run at a lower speed (crawling speed) when it detects no passenger for a set period of time. The crawling speed is usually set at about 0.2m/s, while the rated operating speed is 0.5m/s to 0.75m/s. Various kinds of detection methodologies can be employed for sensing the presence of passenger, such as optical detectors, step sensors, light barriers etc. The detectors for monitoring the approaching passengers can be integrated into a pair of sensing post installed at the entry of the escalator, or they can be incorporated into the handrail entry of the escalator. How it can save energy Service-on-demand escalators are designed to detect the presence of passengers and either stop or slow down when no activity has been detected for a period of time. Hence, energy can be saved when the escalator is idle or operate at lower speed. How much energy can be saved The amount of saving depends on the type of buildings and passenger flow pattern. Based on an measurement carried out by the Electrical and Mechanical Services Department, the energy saving of service-on-demand escalators can be up to 52% and 14% for automatic start/stop and two-speed escalator respectively in an office building. Sources http://www.wisegeek.com/what-is-a-building-envelope.htm http://gbtech.emsd.gov.hk/english/utilize/natural.html http://uol-ventilation.weebly.com/mechanical.html http://gbtech.emsd.gov.hk/english/minimize/daylight.html http://www.cibseenergycentre.co.uk/ventilation.html